1. Technical Field
The present invention relates to an edge detecting device, electronic equipment and an edge detection method for detecting an edge of an object. In particular, the present invention relates to the edge detecting device, the electronic equipment, and the edge detecting method for detecting the edge of the object by analyzing a reflected light from an inspecting region of inspection light emitted to the object arranged in the inspecting region.
2. Background Art
On equipment provided with an image reading function which reads images of a sheet, such as a scanner, a copying machine, a facsimile, a method of determining a sheet size by analyzing a reflected light of a light emitted to the sheet is known as one of methods to detect a sheet edge to determine the sheet size.
For example, an image reader disclosed by a related art 1 (Japanese Patent Application Laid-Open No. 1997-247374) determines the sheet size according to following processes. That is, the image reader illuminates a sheet and detects a reflected light while an apparatus cover is opened. Next, the image reader applies a light to the sheet and detects a reflected light while the apparatus cover is closed. An amount of the reflected light detected by the image reader does not change in an area where the sheet is arranged, since the sheet reflects the emitted light regardless of whether the apparatus cover is opened or closed. On the other hand, an amount of the reflected light detected by the image reader changes in an area where the sheet not arranged, since the emitted light is reflected by the closed apparatus cover while the apparatus cover is closed, and the reflected light is not detected while the apparatus cover is opened and the emitted light passes.
In the related art 1, amounts of the reflected light in a predetermined area when the apparatus cover is opened are determined, and amounts of that when the apparatus cover is closed are determined. Then, the amounts are compared each other. If variation of the amounts exceeds a predetermined threshold value, the sheet edge is detected and the sheet size is determined by judging that the sheet is not arranged in the predetermined area.